Multifunctional experimental system for in-situ simulation of gas hydrate

ABSTRACT

A multifunctional experimental system for in-situ simulation of a gas hydrate includes a computed tomography (CT) scanning device, a reactor, and a pipeline system. The reactor includes: a reactor upper end cover, a reactor lower end cover, a reactor housing and a clamp holder. A first pipeline channel is formed at a top, an upper groove is formed at a bottom, and a first upper joint is arranged in the upper groove. A second pipeline channel is formed at a side, a lower groove is formed at a top, and a first lower joint is arranged in the lower groove; where two ends of the reactor housing are respectively fixed to the reactor upper end cover and the reactor lower end cover. A top end of the clamp holder is provided with a second upper joint, a bottom end of the clamp holder is provided with a second lower joint.

CROSS REFERENCE TO THE RELATED APPLICATIONS

This application is based upon and claims priority to Chinese Patent Application No. 202111532832.4, filed on Dec. 15, 2021, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present application belongs to the technical field of hydrate exploitation, and in particular relates to a multifunctional experimental system for in-situ simulation of a gas hydrate.

BACKGROUND

Gas hydrates are considered to be one of the most potential new green energy sources in the 21st century, which have features such as abundant reserves and clean use. Gas hydrates are formed and stably stored in a high-pressure and low-temperature environment. Due to a special cage-like molecular structure, 1 volume of combustible ice can release 160 volumes of methane in the same pressure state, showing a considerable energy density. As more and more attention is paid to gas hydrates, how to explore and exploit submarine gas hydrates more effectively has become a new topic. Nowadays, countries are facing some difficulties when exploiting gas hydrates. For example, if there is secondary generation of a hydrate in a pipeline, the cementation with silty sediment particles blocks a well casing and thus causes the failure of continuous exploitation, and a geological disaster occurs because a reservoir collapses due to the loss of hydrate cementation as a framework. Therefore, the comprehensive understanding of how a phase state of a gas hydrate changes in sediment pores and even how the saturation, permeability, and other properties of a hydrate reservoir change as an ambient temperature and an ambient pressure change, will greatly increase people's understanding of phase transition properties of the hydrate, thereby providing a guiding basis for the efficient and safe exploitation of the gas hydrate.

Due to the special occurrence nature of hydrates, it is extremely difficult to conduct pressure coring on sediments in a submarine hydrate reservoir, and an in-situ sample transfer process needs to be maintained at a high-pressure and low-temperature state all the way until a sample is in a laboratory device, which results in a high cost and makes it difficult to guarantee supporting facilities. Therefore, the artificial preparation of a hydrate reservoir sediment sample has become an option of general researchers. A mineral composition, a porosity, and a particle size of an artificial sediment sample can be artificially controlled, then methane and water are introduced into the artificial sediment sample, and a high-pressure and low-temperature environment is applied to synthesize a hydrate. This experimental method has the following advantages: A n artificial sample is easier to prepare than a natural sample. Experimental condition variables can be controlled artificially to exclude other interferences and study an influence mechanism of a single condition on the hydrate phase transition, making experimental results more convincing by comparison.

Therefore, the present application provides a multifunctional experimental system for in-situ simulation of a gas hydrate, which allows to comprehensively understand phase transition properties of the gas hydrate and thus provides a guiding basis for the efficient and safe exploitation of the gas hydrate.

SUMMARY

The present application mainly provides a multifunctional experimental system for in-situ simulation of a gas hydrate, which allows to comprehensively understand phase transition properties of the gas hydrate and thus provides a guiding basis for the efficient and safe exploitation of the gas hydrate.

The multifunctional experimental system for in-situ simulation of a gas hydrate provided by the present application includes a computed tomography (CT) scanning device, a reactor, and a pipeline system,

where the CT scanning device is provided with a rotating platform, the reactor is placed on the rotating platform, and the rotating platform is configured to drive the reactor to rotate;

the reactor includes:

a reactor upper end cover, where a first pipeline channel is formed at a top of the reactor upper end cover, at least one upper groove is formed at a bottom of the reactor upper end cover, and a first upper joint is arranged in the upper groove;

a reactor lower end cover, where a second pipeline channel is formed at a side of the reactor lower end cover, at least one lower groove is formed at a top of the reactor lower end cover, and a first lower joint is arranged in the lower groove; and

a reactor housing, where two ends of the reactor housing can be respectively fixed to the reactor upper end cover and the reactor lower end cover to form a sealed first accommodating cavity, and the first accommodating cavity is provided with at least one clamp holder;

the clamp holder has a second accommodating cavity, a top end of the clamp holder is provided with a second upper joint, and a bottom end of the clamp holder is provided with a second lower joint; and the top end of the clamp holder can be embedded into the upper groove to make the second upper joint in butt communication with the first upper joint, and the bottom end of the clamp holder can be embedded into the lower groove to make the second lower joint in butt communication with the first lower joint;

in the pipeline system, an upper pipeline extending into the first pipeline channel is able to communicate with the first upper joint, and a lower pipeline extending into the second pipeline channel is able to communicate with the first lower joint; and in the pipeline system, an upper pipeline extending out of the first pipeline channel is arranged spirally, and a lower pipeline extending out of the second pipeline channel is arranged swirlingly.

The technical solution provided by the present application may include the following beneficial effects: In the present application, reactor end covers are connected to clamp holders through joints, that is, the line connection can be achieved only by docking the first upper joint and the second upper joint and docking the first lower joint and the second lower joint, which can greatly facilitate the safe connection of complicated lines and can enable quick disassembly and assembly. The experimental system of the present application can simulate the synthesis, decomposition, and seepage experiments of gas hydrates in sediments under multiple groups of in-situ reservoir conditions, and can conduct high-accuracy three-dimensional (3D) imaging in real time during an experimental process to observe hydrate forms. The experimental system of the present application ingeniously combines a CT imaging technology, an in-situ high-pressure reactor, and a seepage device, such that researchers can efficiently gain a new understanding of hydrate phase transition.

According to the technical solution of the present application, the reactor can be adapted to a CT scanning device to realize the in-situ synthesis and decomposition of a hydrate and conduct a seepage experiment, and CT can be used to characterize the phase change and pore characteristics of an internal hydrate in real time. Parallel experiments can be conducted on multiple samples at the same time (by arranging multiple sets of clamp holders). In addition, a high-density metal scale is attached to the reactor housing, which can be visualized with a clear contrast in real-time X-ray projection imaging. Numbers on clamp holders facilitate researchers to identify experimental and control groups after scanning selection and reconstruction. The interference of air on hydrate synthesis is eliminated by adding an evacuation system, and the evacuation system is used to check the air tightness of the system pipeline to improve the safety.

It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and should not be construed as a limitation to the present application.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objectives, features, and advantages of the present application will become more apparent from the more detailed description of the exemplary embodiments of the present application in conjunction with the accompanying drawings. In the exemplary embodiments of the present application, the same reference numerals generally refer to the same components.

FIG. 1 is a schematic diagram of a principle structure of a multifunctional experimental system for in-situ simulation of a gas hydrate according to an embodiment of the present application;

FIG. 2 is a schematic structural diagram of the reactor of the multifunctional experimental system according to the present application;

FIG. 3 is a schematic plan view of the reactor of the multifunctional experimental system according to the present application; and

FIG. 4 is a schematic structural diagram of the reactor lower end cover of the multifunctional experimental system according to the present application.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The preferred embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make the present application thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

As mentioned in the background art, the artificial preparation of a hydrate reservoir sediment sample has become an option of general researchers. A mineral composition, a porosity, and a particle size of an artificial sediment sample can be artificially controlled, then methane and water are introduced into the artificial sediment sample, and a high-pressure and low-temperature environment is applied to synthesize a hydrate. At present, researchers generally use a transparent high-pressure reactor to visualize an occurrence state of a hydrate, and 3D imaging is generally achieved through nuclear magnetic resonance (NMR). However, visualization imaging cannot achieve 3D imaging. NMR has low accuracy (generally only reaching the millimeter class), and cannot effectively image sediment pores with a fine-silty particle size. Micro-X-ray microscopy, also known as micro-CT, achieves micro-scale non-destructive 3D imaging of a sample based on the principle that X-rays show different attenuation degrees and present different grayscale images when passing through samples of different densities/average atomic numbers. When the combination of micro-CT with an in-situ high-pressure reactor is used to image an artificial hydrate sediment, real-time in-situ 3D imaging can be achieved on the sediment sample during hydrate formation and decomposition, and different grayscale areas can be segmented through image processing to obtain a variation rule of a hydrate in a pore structure and variation rules of parameters such as effective permeability and saturation of the sediment.

In order to comprehensively understand phase transition properties of a gas hydrate and provide a guiding basis for the efficient and safe exploitation of the gas hydrate, an experimental system for in-situ simulation of a gas hydrate is provided in this embodiment. The experimental system can use the 3D imaging of a CT scanning device (the CT scanning device achieves micro-scale non-destructive 3D imaging of a sample based on the principle that X-rays show different attenuation degrees and present different grayscale images when passing through samples of different densities/average atomic numbers) to achieve the real-time 3D characterization of a phase structure of a gas hydrate in pores during synthesis and decomposition thereof and the real-time 3D characterization of saturation and effective permeability of the hydrate of the sediment, such as to obtain influence mechanisms of the temperature, pressure, sediment particle size and porosity, and the like on hydrate phase transition. Moreover, by measuring several groups of samples at the same time, the efficiency of the contrast experiment is improved, and the reaction conditions of the contrast experiment are also guaranteed to be consistent.

The technical solutions of the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

Reference is made first to FIG. 1 , and FIG. 1 is a schematic diagram of a principle structure of a multifunctional experimental system for in-situ simulation of a gas hydrate according to an embodiment of the present application. The experimental system provided by the present application mainly includes a CT scanning device, a reactor, and a pipeline system. In FIG. 1 , a part inside a dashed box is mainly the CT scanning device and the reactor, and a part outside the dashed box is mainly the pipeline system. In this embodiment, the CT scanning device mainly includes an X-ray source 11, an X-ray receiver 12, and a rotating platform 13 arranged between the X-ray source 11 and the X-ray receiver 12, and the reactor is arranged on the rotating platform 13. In this embodiment, the pipeline system mainly includes a confining pressure liquid pipeline system, a gas delivery pipeline system, a water delivery pipeline system, a gas/liquid recovery pipeline system, an evacuation pipeline system, and the like. These pipeline systems cooperate with the reactor and the CT scanning device to realize an in-situ simulation experiment of a gas hydrate, such as to comprehensively understand phase transition properties of the gas hydrate and provide a guiding basis for the efficient and safe exploitation of the gas hydrate.

A structure of the reactor of this embodiment will be described in detail below with reference to FIG. 2 to FIG. 4 , and then a working principle of the experimental system of this embodiment will be further described with reference to the pipeline system. FIG. 2 is a schematic structural diagram of the reactor of the multifunctional experimental system according to the present application; FIG. 3 is a schematic plan view of the reactor of the multifunctional experimental system according to the present application; and FIG. 4 is a schematic structural diagram of the reactor lower end cover of the multifunctional experimental system according to the present application.

As shown in FIG. 2 to FIG. 4 , in this embodiment, the reactor mainly includes a reactor upper end cover 21, a reactor lower end cover 22, a reactor housing 23, and a clamp holder 24. Two ends of the reactor housing 23 can be respectively fixed to the reactor upper end cover 21 and the reactor lower end cover 22 to form a sealed first accommodating cavity, at least one clamp holder 24 is arranged in the first accommodating cavity, and the clamp holder 24 is configured for the generation or decomposition of a gas hydrate. The pipeline system can provide corresponding experimental conditions for the clamp holder to achieve the generation or decomposition of a gas hydrate in an in-situ environment. The in-situ environment can be understood as that the experiments and measurements are conducted in an environment at which an object to be measured is originally located. That is, the multifunctional experimental system of this embodiment can simulate the characteristics of the gas hydrate in the in-situ environment to improve the experimental value of experimental data.

In FIG. 2 , the reactor lower end cover 22 is fixedly arranged on the rotating platform 13 (as an example, the reactor lower end cover 22 can be screwed to the rotating platform 13 through threaded connection), such that the entire reactor is fixed between the X-ray source 11 and the X-ray receiver 12. In this way, the rotating platform 13 can drive the reactor to rotate, and after the X-ray source 11 is turned on, real-time X-rays pass through the reactor housing 23 and the clamp holder 24 and are projected on the X-ray receiver 12 to achieve projection imaging, such that an internal state of the clamp holder 24 can be observed. A specific principle of the CT scanning device will not be described here. In a specific embodiment, the CT scanning device can usually be wrapped in a lead shell as a whole (the dashed box in FIG. 1 can represent a lead shell area) to shield X-ray radiation, and a pipeline outside the dashed box needs to pass through a preset radiation shielding maze when entering the CT scanning device, which enables pipeline channels inside and outside the CT scanning device and can also ensure that X-rays will not leak to the outside of the CT scanning device 1 to cause harm to personnel. For convenience of description, the lead shell wrapped around the CT scanning device is omitted in this embodiment.

As shown in FIG. 2 to FIG. 4 , a first pipeline channel 211 is formed at a top of the reactor upper end cover 21, at least one upper groove 210 is formed at a bottom of the reactor upper end cover 21, and a first upper joint 2101 is arranged in the upper groove 210. A second pipeline channel 221 is formed at a side of the reactor lower end cover 22, at least one lower groove 220 is formed at a top of the reactor lower end cover 22, and a first lower joint 2201 is arranged in the lower groove 220. A second upper joint 2410 is arranged at a top end of the clamp holder 24, and a second lower joint 2420 is arranged at a bottom end of the clamp holder 24. The top end of the clamp holder 24 can be embedded into the upper groove 210, such that the second upper joint 2410 is in butt communication with the first upper joint 2101, and the bottom end of the clamp holder 24 can be embedded into the lower groove 220, such that the second lower joint 2420 is in butt communication with the first lower joint 2201. That is, a plurality of grooves are formed in the reactor upper end cover 21 and the reactor lower end cover 22 separately, a first joint is pre-arranged in the groove, two ends of the clamp holder are each provided with a second joint matching the first joint, and the two ends of the clamp holder are respectively embedded into the grooves of the reactor upper end cover 21 and the reactor lower end cover 22, such that the first joint and the second joint are in butt communication. Two clamp holders 24 are shown in FIG. 2 , four clamp holders 24 are shown in FIG. 3 , and a structure of the reactor lower end cover 22 shown in FIG. 4 includes four lower grooves 220. Those skilled in the art can understand that the number of clamp holders 24 can be set according to actual needs, and accordingly, upper grooves 210 and lower grooves 220 equal in number to the clamp holders 24 need to be correspondingly formed on the reactor upper end cover 21 and the reactor lower end cover 22, and two ends of each clamp holder 24 are respectively embedded in an upper groove 210 and a lower groove 220.

In a specific example, the first upper joint 2101 and/or the second upper joint 2410 may be provided with a first locking mechanism, and the first locking mechanism can lock the first upper joint 2101 and the second upper joint 2410 after the first upper joint 2101 is docked with the second upper joint 2410. For example, the first upper joint 2101 and the second upper joint 2410 can be each provided with a matching snap structure as the first locking mechanism, and the first upper joint 2101 and the second upper joint 2410 can be locked by the matching snap structure. Similarly, the first lower joint 2201 and/or the second lower joint 2420 may be provided with a second locking mechanism, and the second locking mechanism can lock the first lower joint 2201 and the second lower joint 2420 after the first lower joint 2201 is docked with the second lower joint 2420. For example, the first lower joint 2201 and the second lower joint 2420 can be each provided with a matching snap structure as the second locking mechanism, and the first lower joint 2201 and the second lower joint 2420 can be locked by the matching snap structure. Specific designs of the first locking mechanism and the second locking structure are not limited in this embodiment, provided that, after the first upper joint 2101 and the second upper joint 2410 are docked and the first lower joint 2201 and the second lower joint 2420 are docked, the mutual locking can be achieved.

In a more specific example, an inner wall of the upper groove 210 is provided with a third locking mechanism 2100, and after the clamp holder 24 is embedded into the upper groove 210, the first upper joint 2101 is docked with the second upper joint 2410 (at which point the first locking mechanism can lock the first upper joint 2101 and the second upper joint 2410), and the second locking mechanism 2100 can lock a part of the clamp holder 24 entering the upper groove 210; and similarly, an inner wall of the lower groove 220 is provided with a fourth locking mechanism 2200, and after the clamp holder is embedded in the lower groove 220, the first lower joint 2201 is docked with the second lower joint 2420, and the fourth locking mechanism 2200 can lock a part of the clamp holder 24 entering the lower groove 220. In this way, the clamp holder 24 can be fixed by the third locking mechanism 2100 and the fourth locking mechanism 2200. As an example, the third locking mechanism 2100 and the fourth locking mechanism 2200 may be clip-set locking structures arranged at inner sides of the upper groove 210 and the lower groove 220, respectively. Specific structures of the third locking mechanism 2100 and the fourth locking mechanism 2200 are not limited in this embodiment, provided that, after the clamp holder 24 is embedded into the upper groove 210 and the clamp holder 24 enters the lower groove 220, the clamp holder 24 can be locked.

As shown in FIG. 2 to FIG. 3 , in this embodiment, the clamp holder 24 includes a clamp-holder upper end cover 241, a clamp-holder lower end cover 242, and a porous shell 243. A second upper joint 2410 of the clamp holder 24 may be arranged at a top of the clamp-holder upper end cover 241, and a second lower joint 2420 of the clamp holder 24 may be arranged at a bottom of the clamp-holder lower end cover 242. The porous shell 243 is a clamp-holder shell 243 with multiple pores, where two ends of the porous shell 243 can be respectively fixed to the clamp-holder upper end cover 241 and the clamp-holder lower end cover 242 to form a sealed second accommodating cavity, and the second accommodating cavity is pre-filled with a sediment sample. As an example, the clamp-holder lower end cover 242 can be screwed to one end of the porous shell 243, then the second accommodating cavity can be filled with a sediment sample and the sediment sample can be fully compacted using a tool such as a small hammer, and then the clamp-holder upper end cover 241 is fixed to the other end of the porous shell 243 by screwing. A rubber ring is embedded at inner sides of the clamp-holder upper end cover 241 and the clamp-holder lower end cover 242, which can be tightly combined with the rubber sleeve 244 on the inner wall of the porous shell 243 of the clamp holder 24 through the rubber ring. An area A in FIG. 3 is a top view of the reactor after being cross-cut from the middle, and four clamp holders 24 are shown in the area A, where a rubber sleeve 244 is attached to an inner wall of the porous shell 243 of each clamp holder 24, that is, the rubber sleeve 244 surrounds the second accommodating cavity, and a confining pressure space 200 is formed between the outer wall of the porous shell 243 and the inner wall of the reactor housing 23. A confining pressure liquid in the confining pressure space 200 can generate a pressure on the rubber sleeve 244 through the pores of the porous shell 243, which in turn acts on the second accommodating cavity in the clamp holder 24. Further, the reactor may further include a rubber sealing sleeve, and the rubber sealing sleeve may be configured to achieve the sealing between the porous shell 243 and the upper groove 210 and the sealing between the porous shell 243 and the lower groove 220 after the clamp holder 24 is embedded into the upper groove 210 and the lower groove 220. In this way, the confining pressure liquid in the confining pressure space can be prevented from leaking.

Further, an area B of FIG. 3 is a schematic diagram of an inner side of the clamp-holder upper end cover. In this embodiment, a target-shaped first groove 2412 is formed at an inner side of the clamp-holder upper end cover 241, and a target-shaped second groove is formed at an inner side of the clamp-holder lower end cover 242 (the second groove has the same structure as the first groove 2412). Centers of the first groove 2412 and the second groove 2412 communicate with the second upper joint 2410 and the second lower joint 2420, respectively. In this way, the first upper joint is docked with the second upper joint, such that a gas or liquid entering the second accommodating cavity through the second upper joint can evenly diffuse; and similarly, the first lower joint is docked with the second lower joint, such that a gas or liquid entering the second accommodating cavity through the second lower joint can evenly diffuse.

As shown in FIG. 2 , in a more specific embodiment, a metal scale 231 is formed on an outer surface of the reactor housing 23, and correspondingly, the reactor housing 23 and the porous shell 243 of the clamp holder 24 can be made of a polymer composite. Such a polymer composite has excellent mechanical properties and can withstand a confining pressure exerted by the confining pressure liquid and a pore pressure from a sediment inside the rubber sleeve, and a reactor housing with such a density can have a small impact on the penetration of X-rays during CT scanning and reduce the interference on the penetration of X-rays through a sample. Since a density of the metal scale 231 is much higher than that of the reactor housing 23 and the porous shell 243 made of polymer materials and the sediment, the attenuation of the metal scale 231 to X-rays is a much higher than that of other areas of the reactor 2, and thus scales with a clear contrast (dark color) can be seen from the projection. With the metal scale 231, a gas hydrate sediment area included in a current view field can be obtained without conducting 3D scanning and reconstruction, thereby assisting in selecting a scanning area and improving the efficiency of an experimenter. When X-ray CT scanning is conducted, a scanning view field can be changed by changing relative distances among the X-ray source 11, the reactor, and the X-ray receiver 12, such that sediments in the four sets of clamp holders in the reactor can be simultaneously scanned or a set of clamp holders 24 can also scanned separately. In addition, an outer surface of each clamp holder 24 (namely, the outer surface of the porous shell 243) can also be marked with a number made of a metal, which is convenient for identification during X-ray selective scanning. Specifically, when four sets of clamp holders are used for test at the same time, the clamp holders are marked as 1, 2, 3, and 4. According to different experimental purposes, samples filled in the four sets of clamp holders can be: 1. four groups of sediment samples with the same composition and particle size, where an equal amount of water and methane at the same pressure are injected, and each core clamp holder in the reactor is observed and recorded under the same confining pressure and temperature conditions to reduce the influence of experimental randomness on experimental results; and 2. four groups of sediment samples with different mineral compositions or particle sizes, which is intended to observe the difference in effects of a sediment on hydrate phase transition, effective permeability, and saturation. In this embodiment, the clamp holder 24 is insulated from the reactor housing 23 to avoid interference during resistivity measurement. The reactor upper end cover 21, the reactor lower end cover 22, the clamp-holder upper end cover 241, and the clamp-holder lower end cover 242 may be made of aluminum alloy.

As shown in FIG. 2 to FIG. 4 , in the pipeline system, an upper pipeline 301 (with reference to 301 shown in FIG. 3 ) extending into the first pipeline channel 211 can communicate with the first upper joint 2101, and a lower pipeline 302 (with reference to 302 shown in FIG. 3 ) extending into the second pipeline channel 221 can communicate with the first lower joint 2201; and in the pipeline system, an upper pipeline 301 (with reference to 301 shown in FIG. 2 ) extending out of the first pipeline channel 211 may be arranged spirally, and a lower pipeline 302 (with reference to 302 shown in FIG. 2 ) extending out of the second pipeline channel 221 may be arranged swirlingly. In this way, the upper pipeline 301 can communicate with the second upper joint 2410 only by docking the first upper joint 2101 with the second upper joint 2410, the lower pipeline 302 can communicate with the second lower joint 2420 only by docking the first lower joint 2201 with the second lower joint 2420, and then a pipeline system that needs to communicate with the second accommodating cavity in the clamp holder 24 can communicate with the upper pipeline 301 and/or the lower pipeline 302, which simplifies the pipeline connection in the pipeline system, reduces the risk of gas and liquid leakage, and increases the reliability of the experimental system. In this embodiment, an upper pipeline 301 extending out of the first pipeline channel 211 is arranged spirally (a structure similar to a spring coil), and a lower pipeline 302 extending out of the second pipeline channel 221 is arranged swirlingly (a structure similar to a mosquito coil); and during an experiment, the rotating platform 13 drives the reactor to rotate (the rotating platform 13 can rotate in a range of -180° to 180° , that is, it can rotate by 360° to make the CT scanning device conduct a multi-angle scanning on the reactor, which can drive the spiral upper pipeline 301 and the swirled lower pipeline 302 to rotate, such that the pipelines of the pipeline system do not affect the rotation of the reactor. As an example, the first pipeline channel 211 and the reactor upper end cover 21 may be arranged at an acute angle to further reduce the interference of the pipelines to the rotation of the reactor. The second pipeline channel 221 is drawn out from a side of the reactor lower end cover 22, which is also for the convenience of rotation.

The working principle of the experimental system of this embodiment will be further described below with reference to FIG. 1 .

As shown in FIG. 1 , in this embodiment, the pipeline system mainly includes a confining pressure liquid pipeline system, a gas delivery pipeline system, a water delivery pipeline system, a gas/liquid recovery pipeline system, and an evacuation pipeline system.

The confining pressure liquid pipeline system can inject a confining pressure liquid of a preset temperature and a preset pressure into the confining pressure space 200. Specifically, as shown in FIG. 1 , the confining pressure liquid pipeline system includes a first confining pressure liquid pipeline 311 and a second confining pressure liquid pipeline 312; one end of the first confining pressure liquid pipeline 311 is connected to a confining pressure liquid cylinder 310, and the other end of the first confining pressure liquid pipeline 311 extends into the confining pressure space 200 from the first pipeline channel 211; and one end of the second confining pressure liquid pipeline 312 is connected to a confining pressure liquid cylinder 310, and the other end of the second confining pressure liquid pipeline 312 extends into the confining pressure space 200 from the second pipeline channel 221. The confining pressure liquid cylinder 310 is provided with a first water-bath temperature-control device 3101, and the first water-bath temperature-control device 3101 is configured to adjust a temperature of the confining pressure liquid. A first gate valve 313, a first liquid-pressure gauge 314, and a first servo loading pump 315 are also provided on the first confining pressure liquid pipeline 311 or the second confining pressure liquid pipeline 312, where the first gate valve 313 is configured to open or block the first confining pressure liquid pipeline 311 and the second confining pressure liquid pipeline 312; the first liquid-pressure gauge 314 is configured to measure a pressure of the confining pressure liquid; and after the confining pressure liquid reaches a preset temperature, the first gate valve 313 is opened, and the first servo loading pump 315 can cyclically load the confining pressure liquid, such that the confining pressure liquid can reach a preset pressure and the clamp holder 24 is in an in-situ environment. Specifically, during an experiment, the first water-bath temperature-control device 3101 can be started to reduce a temperature of the confining pressure liquid to a hydrate generation temperature (such as 4° C.), then the first gate valve 313 and the first servo loading pump 315 can be opened to start to cyclically load the confining pressure liquid, and the pressure of the confining pressure liquid is slowly increased to a required pressure, where the required pressure of the confining pressure is a sum of a pore pressure provided by methane in the clamp holder 24 and a simulated formation pressure, such that a confining pressure on the rubber sleeve in the clamp holder 24 is equal to a pressure in the formation. A part of the first confining pressure liquid pipeline 311 extending out of the first pipeline channel 211 is arranged spirally, and a part of the second confining pressure liquid pipeline 312 extending out of the second pipeline channel 221 is arranged swirlingly. The confining pressure liquid is adopted for cooling in this embodiment, which can simplify the system, prevent X-rays from attenuating due to too much interference, and make a ray source as close to a core as possible to obtain high resolution and prominent signal-noise ratio (SNR). The confining pressure liquid above can be aviation silicone oil. The gas delivery pipeline system can deliver a gas from two ends of the clamp holder 24 to the second accommodating cavity of the clamp holder 24. Specifically, as shown in FIG. 1 , the gas delivery pipeline system includes a main gas delivery pipeline 321; one end of the main gas delivery pipeline 321 is connected to a methane cylinder 322, and the other end of the main gas delivery pipeline 321 is connected to one end of a first gas delivery pipeline 324 and one end of a second gas delivery pipeline 325 through a first three-way valve 323; and the other end of the first gas delivery pipeline 324 communicates with the upper pipeline 301 through a four-way valve 300, and the other end of the second gas delivery pipeline 325 communicates with the lower pipeline 302 through a second three-way valve 3214. Further, a pressure-reducing valve 3211, a gas pressure-stabilizing pump 3212, and a first gas-flow meter 3213 are also provided on the main gas delivery pipeline 321; a second gate valve 3241 and a first gas-pressure gauge 3242 are provided on the first gas delivery pipeline 324; and a third gate valve 3251 and a second gas-pressure gauge 3252 are provided on the second gas delivery pipeline 325. The pressure-reducing valve 3211 can adjust a gas pressure output from the methane cylinder 322 to an adjustment range of the gas pressure-stabilizing pump 3212; the gas pressure-stabilizing pump 3212 is configured to adjust a gas flow into the clamp holder; the second gate valve 3241 and the third gate valve 3251 are respectively configured to open or block the first gas delivery pipeline 324 and the second gas delivery pipeline 325; and the first gas-pressure gauge 3242 and the second gas-pressure gauge 3252 are respectively configured to measure pressure values of gases passing through the first gas delivery pipeline 324 and the second gas delivery pipeline 325. Specifically, during an experiment, the methane cylinder 322 can also be opened during the injection of the confining pressure liquid (that is, the confining pressure and the pore pressure (namely, the methane pressure) are applied at the same time, and the confining pressure is always higher than the methane pressure (2 MPa) during the application process), the pressure-reducing valve 3211 is used to reduce the gas pressure output from the methane cylinder 322 to the adjustment range of the gas pressure-stabilizing pump 3212, the gas pressure-stabilizing pump 3212 is adjusted to make the pore pressure of the sediment in the clamp holder slowly increase to a pressure required for the generation of a methane hydrate, and the gas pressure-stabilizing pump 3212 can adjust a gas flow according to the real-time gas pressure of a pipeline at a side of the reactor to make a connecting pipeline at a side of the reactor under a stable pressure. The first three-way valve 323, the second gate valve 3241, and the third gate valve 3251 are opened, the first gas delivery pipeline 324 is allowed to communicate with the upper pipeline 301 through the four-way valve 300, and the second gas delivery pipeline 325 is allowed to communicate with the lower pipeline 302 through the second three-way valve 3214, such that upper and lower ends of the clamp holder 24 are simultaneously introduced with isobaric methane gases. The upper and lower ports of the reactor are introduced with gases simultaneously to increase a contact area between methane and water and improve the hydrate synthesis efficiency. The first gas-flow meter 3213 is started to record a methane amount consumed in the generation of a hydrate.

The water delivery pipeline system can deliver a liquid from a bottom end of the clamp holder 24 to the second accommodating cavity of the clamp holder 24. Specifically, as shown in FIG. 1 , the water delivery pipeline system includes a water delivery pipeline 331; and one end of the water delivery pipeline 331 communicates with the lower pipeline 302 through the second three-way valve 3214, and the other end of the water delivery pipeline 331 is connected to a deionized water cylinder 330. The deionized water cylinder 330 is provided with a second water-bath temperature-control device 3301, and the second water-bath temperature-control device 3301 is configured to adjust a temperature of the deionized water. A fourth gate valve 3311 (one or two may be provided, and in this embodiment, as shown in FIG. 1 , two fourth gate valves 3311 are provided), a second liquid-pressure gauge 3312, a second servo loading pump 3313, and a first liquid-flow meter 3314 are also provided on the water delivery pipeline 331, where the fourth gate valve 3311 is configured to open or block the water delivery pipeline 331, the second liquid-pressure gauge 3312 is configured to measure a pressure of deionized water, the second servo loading pump 3313 is configured to inject deionized water into a clamp holder body, and the first liquid-flow meter 3314 is configured to record an amount of deionized water injected. During an experiment, the second water-bath temperature-control device 3301 is started to reduce the temperature of deionized water to the hydrate synthesis temperature, then the fourth gate valve 3311 and the second servo loading pump 3313 are opened, and the water delivery pipeline 331 is allowed to communicate with the lower pipeline 302 through the second three-way valve 3214, such as to start to inject low-temperature deionized water into the clamp holder. According to an experimental purpose, a water injection amount is adjusted to control hydrate generation conditions (water saturation/gas saturation), the first liquid-flow meter 3314 is used to control the water injection amount, and when the water injection amount reaches a required value, the fourth gate valve 3311 and the second servo loading pump 3313 are closed.

The gas/liquid recovery pipeline system can recover a gas and/or a liquid decomposed from the second accommodating cavity of the clamp holder 24. Specifically, as shown in FIG. 1 , the gas/liquid recovery pipeline system includes a gas/liquid recovery pipeline, and the gas/liquid recovery pipeline includes a main recovery pipeline 341, a gas recovery pipeline 342, and a liquid recovery pipeline 343. One end of the main recovery pipeline 341 communicates with the upper pipeline 301 through a four-way valve 300, and the other end is connected to a gas-liquid separation device 344; one end of the gas recovery pipeline 342 is connected to the gas-liquid separation device 344, and the other end is connected to a gas recovery bottle 345; and one end of the liquid recovery pipeline 343 is connected to the gas-liquid separation device 344, and the other end is connected to a liquid recovery bottle 346. A fifth gate valve 3411 and a back-pressure valve 3412 are provided on the main recovery pipeline 341, a sixth gate valve 3421 and a second gas-flow meter 3422 are provided on the gas recovery pipeline 342, and a second liquid-flow meter 3431 is provided on the liquid recovery pipeline 343.

The evacuation pipeline system is configured to evacuate each pipeline of the pipeline system. Specifically, as shown in FIG. 1 , the evacuation pipeline system includes an evacuation pipeline 351, where one end of the evacuation pipeline 351 is connected to a vacuum pump 350, and the other end is connected to the upper pipeline 301 through a four-way valve 300. Moreover, since the first gas delivery pipeline 324 and the main recovery pipeline 341 also communicate with the upper pipeline 301 through a four-way valve 300, the four-way valve 300 can be adjusted according to experimental needs, such that the evacuation pipeline 351, the first gas delivery pipeline 324, the main recovery pipeline 341, and the upper pipeline 301 can communicate with each other according to experimental needs. Further, a seventh gate valve 3511 and a third gas-pressure gauge 3512 are also provided on the evacuation pipeline 351, and the seventh gate valve is configured to open or block the evacuation pipeline 351. When all pipeline systems are connected, the evacuation system is used for an evacuation operation before an experiment starts. Specifically, the pressure-reducing valve 3211, the fourth gate valve 3311, and the first gate valve 313 are first closed, then all other gates of the pipeline system are opened (at which point the four-way valve 300 is adjusted such that the evacuation pipeline 351 communicates with the first gas delivery pipeline 324, the main recovery pipeline 341, and the upper pipeline 301), and the vacuum pump 350 is started until a reading of each gas-pressure gauge in the experimental system drops to 0. The experimental system stands and is observed for a period of time (usually two hours). If there is no change in a reading of each gas-pressure gauge everywhere, it means that the air tightness of the system is intact, the evacuation of the whole system is completed, and the interference of air on the hydrate synthesis is eliminated. After the check is completed, the gate valve 3511 is closed, all gate valves in the system are closed, and an experiment is getting started.

In the above-mentioned pipeline system, the upper pipeline 301 is arranged spirally, and the lower pipeline 302 is arranged swirlingly. In this way, the pipelines of the pipeline system will not affect the overall 360-degree rotation of the reactor during scanning, while the rotation of the reactor will not cause bending damage or a stress concentration effect to a metal high-pressure gas/liquid pipeline. Further, the pipelines of the above-mentioned pipeline system can also be wrapped with a heat-insulating material to avoid heat transfer, thereby avoiding mutual influence among the pipelines. In addition, ends of the upper pipeline 301 and the lower pipeline 302 may also be covered with a gauze, and the covering gauze can prevent sediment particles from entering the upper pipeline 301 and the lower pipeline 302 to block the pipelines.

Experimental steps of hydrate generation and scanning are as follows: The first water-bath temperature-control device 3101 is started to reduce a temperature of the confining pressure liquid to a hydrate generation temperature, then the first gate valve 313 and the first servo loading pump 315 are opened to start to cyclically load the confining pressure liquid, and the pressure of the confining pressure liquid is slowly increased to a required pressure, where the required pressure of the confining pressure is a sum of a pore pressure provided by methane in the clamp holder and a simulated formation pressure, such that a confining pressure on the rubber sleeve in the clamp holder is equal to a pressure in the formation. The methane cylinder 322 can also be opened, the pressure-reducing valve 3211 is used to reduce the gas pressure in the methane cylinder to the adjustment range of the gas pressure-stabilizing pump 3212, the gas pressure-stabilizing pump 3212 is adjusted to make the pore pressure of the sediment in the clamp holder slowly increase to a pressure required for the generation of a methane hydrate (which needs to be higher than an equilibrium pressure of the hydrate phase, and generally can be 6 MPa to 15 MPa), and the gas pressure-stabilizing pump 3212 can adjust a gas flow according to the real-time gas pressure of a pipeline at a side of the reactor 2 to make a connecting pipeline at a side of the reactor under a stable pressure. The three-way valve 323, the second gate valve 3241, and the third gate valve 3251 are opened, such that the upper and lower ends of the clamp holder in the reactor 2 are simultaneously introduced with isobaric methane gases; and the first gas-flow meter 3213 is started to record a methane amount consumed in the generation of the hydrate.

The second water-bath temperature-control device 3301 is started to reduce the temperature of deionized water to the hydrate synthesis temperature, then the fourth gate valve 3311 and the second servo loading pump 3313 are opened to start to inject low-temperature deionized water into the clamp holder. According to an experimental purpose, a water injection amount is adjusted to control hydrate generation conditions (water saturation/gas saturation), the first liquid-flow meter 3314 is used to control the water injection amount, and when the water injection amount reaches a required value, the fourth gate valve 3311 and the second servo loading pump 3313 are closed.

When the reading of the first gas-flow meter 3213 does not increase temporarily and the temperature and pressure at two ends of the clamp holder are stabilized at set values for a period of time, methane has filled the clamp holder and is dissolved in water in a saturated state, at which point the synthesis of the methane hydrate begins. During the synthesis process, the clamp holder is always maintained at a ventilation state, the first gas-flow meter 3213 records a gas flow of ventilation into the clamp holder in real time, and the gas pressure-stabilizing pump 3212 maintains a methane pressure in the clamp holder (that is, the sediment pore pressure) at a set value. The X-ray source 11 is turned on, and real-time X-rays are allowed to pass through the reactor and the clamp holder and are projected on the X-ray receiver 12 to achieve projection imaging, such that an internal state of the clamp holder can be observed. Since a density of the metal scale 231 is much higher than that of the reactor housing and the clamp-holder porous shell made of polymer materials and the sediment, the attenuation of the metal scale to X-rays is a much higher than that of other areas of the reactor, and thus scales with a clear contrast (dark color) can be seen from the projection. With the scale, a hydrate sediment area included in a current view field can be obtained without conducting 3D scanning and reconstruction, thereby assisting in selecting a scanning area and improving the efficiency of an experimenter. When X-ray CT scanning is conducted, a scanning view field can be changed by changing relative distances among the X-ray source 11, the reactor 2, and the X-ray receiver 12, such that sediments in the four sets of clamp holders in the reactor 2 can be scanned simultaneously or a set of clamp holders can scanned separately. That is, the whole area of cores in the four sets of clamp holders can be roughly scanned with relatively low resolution, and a specified section of sediment in a specified area can be finely scanned with high resolution.

When it is observed that the reading of the first gas-flow meter 3213 starts to increase once again, it indicates that the hydrate in the clamp holder has passed an induction period and a large amount of hydrate begins to be generated. After a period of time (usually about one week), when the reading of the first gas-flow meter 3213 does not change once again, it can be considered that the hydrate in the sediment has reached saturation at this time. In a process from hydrate generation after the induction period to hydrate saturation, hydrates can be subjected to parallel comparison in terms of hydrate generation time and hydrate saturation time to study the effects of different sediments on hydrate generation. In a hydrate synthesis process, multiple X-ray CT scans are conducted at specified time points, and 3D grayscale images reconstructed according to the scans are segmented to calculate a saturation of a hydrate in sediment pores and observe the change characteristics in sediment pores during hydrate formation.

The above is an overall structural design of the experimental system provided by the present application. In a design of the entire pipeline system, only the upper pipeline 301 is connected to the first upper joint 2101 through the first pipeline channel 211, while other pipelines in the pipeline system communicate with the upper pipeline 301 through a four-way valve 300; and similarly, only the lower pipeline 302 is connected to the first lower joint 2201 through the second pipeline channel 221, while other pipelines in the pipeline system communicate with the lower pipeline 302 through a second three-way valve 3214. In this way, the safe connection of complicated lines can be greatly facilitated, and the disassembly and assembly can be achieved quickly. In addition, when a specified pipeline system needs to communicate with the second accommodating cavity in the clamp holder 24, it is only necessary to make its pipelines communicate with the upper pipeline 310 and/or the lower pipeline 302 by adjusting the four-way valve 300 and/or the second three-way valve 3214. In the following description, the adjustment of the four-way valve 300 and the second three-way valve 3214 will default to adaptive adjustment, and how to adjust the four-way valve 300 and the second three-way valve 3214 will not be described separately.

Methods for conducting the experiment under different conditions in this embodiment will be briefly described below:

Experimental steps of hydrate decomposition and scanning can be achieved by a depressurization method, a heat injection method, a heating method, and a reagent injection method.

Depressurization method: After a hydrate saturation reaches the maximum value, the three-way valve 323 is closed, and the fifth gate valve 3411 and the sixth gate valve 3421 are opened; and a pressure of the back-pressure valve 3412 is set to be lower than an internal pore pressure of the clamp holder, the pressure is slightly reduced by the same amount at regular intervals to achieve a stepwise pressure reduction (for example, a gradient of 0.5 MPa is adopted), and the decomposition of a hydrate in a sediment is observed by CT scanning. During the pressure-reduction process, a confining pressure maintained is also reduced accordingly by adjusting the first servo loading pump 315, such that a relative confining pressure on the clamp holder remains constant. Methane produced from the decomposition is recovered into the gas recovery bottle 345. The hydrate decomposition reactions in different clamp holders are compared to study the effects of different sediments on the phase transition of hydrate decomposition.

Heat injection method: After a hydrate saturation reaches the maximum value, the three-way valve 323 is closed, and the fifth gate valve 3411 is opened; a temperature of the second water-bath temperature-control device 3301 is set to be higher than a temperature of a confining pressure water bath, and the fourth gate valve 3311 and the second servo loading pump 3313 are opened to inject deionized water into the clamp holder at a specified pressure; and the sixth gate valve 3421 is opened, and the hydrate decomposition in a sediment is observed by CT scanning. During the decomposition process, the changes of readings of the first gas-pressure gauge 3242 and the second gas-pressure gauge 3252 are observed, and a confining pressure maintained is also reduced accordingly by adjusting the first servo loading pump 315, such that a relative confining pressure on the clamp holder remains constant. Methane and water produced from the decomposition are recovered into the gas recovery bottle 345 and the liquid recovery bottle 346, respectively.

Heating method: After a hydrate saturation reaches the maximum value, the three-way valve 323 is closed, and the fifth gate valve 3411 and the sixth gate valve 3421 are opened. A temperature of the first water-bath temperature-control device 3101 is set to rise (for example, a set temperature rises in a gradient of 0.5° C.), and the clamp holder is heated accordingly. During the hydrate decomposition process, the changes of readings of the first gas-pressure gauge 3242 and the second gas-pressure gauge 3252 are observed, and a confining pressure maintained is also reduced accordingly by adjusting the first servo loading pump 315, such that a relative confining pressure on the clamp holder remains constant. The hydrate decomposition in a sediment is observed by CT scanning. Methane and water produced from the decomposition are recovered into the gas recovery bottle 345 and the liquid recovery bottle 346, respectively.

Reagent injection method: After a hydrate saturation reaches the maximum value, the three-way valve 323 is closed; a solution in the deionized water cylinder 31 is replaced with a chemical reagent used in the exploitation of combustible ice by a reagent injection method, and the fifth gate valve 3411 is opened; a temperature of the water-bath temperature-control device is set to be equal to a temperature of a confining pressure water bath, and the fourth gate valve 3311 and the second servo loading pump 3313 are opened to inject the chemical reagent into the clamp holder at a specified pressure; and the sixth gate valve 3421 is opened, and the hydrate decomposition in a sediment is observed by CT scanning. During the decomposition process, the changes of readings of the first gas-pressure gauge 3242 and the second gas-pressure gauge 3252 are observed, and a confining pressure maintained is also reduced accordingly by adjusting the first servo loading pump 315, such that a relative confining pressure on the clamp holder remains constant. Methane and water produced from the decomposition are recovered into the gas recovery bottle 345 and the liquid recovery bottle 346, respectively.

Experimental steps of a seepage experiment and scanning are as follows: When a hydrate is at a specified synthesis or decomposition stage, the gas supply to the clamp holder is suspended, and the second gate valve 3241 and the third gate valve 3251 are closed; the fourth gate valve 3311 and the fifth gate valve 3411 are opened, the back-pressure valve 3412 is adjusted to the internal pore pressure of the clamp holder, and the second servo loading pump 3313 is opened to inject deionized water at a constant speed and a pressure higher than the pore pressure; the deionized water enters the clamp holder along the water delivery pipeline and then flows out through the main recovery pipeline, and the liquid-pressure sensor on the clamp-holder end cover records a pressure difference between two ends; and the fluid enters the gas-liquid separation device 344 from the clamp holder, and the second gas-flow meter 3422 and the second liquid-flow meter 3431 record seepage gas and liquid amounts, respectively, such that an effluent flow rate of the seepage experiment can be obtained. The effective permeability of a hydrate sediment is calculated according to the Darcy's law. Methane and water produced from the seepage are recovered into the gas recovery bottle 345 and the liquid recovery bottle 346, respectively. Optionally, each of the four sets of clamp holders may be equipped with a separate seepage and measurement device system. It can be seen that the experimental system of the present application ingeniously combines a CT imaging technology, an in-situ high-pressure reactor, and a seepage device, such that researchers can efficiently gain a new understanding of hydrate phase transition.

In the above, different experimental purposes can be achieved by controlling the gate valves and the servo loading pumps of the pipeline system.

The experimental system of this embodiment may further include a data acquisition system. As shown in FIG. 1 , the data acquisition system includes a data acquisition unit 361, a first data line 362, a second data line 363, and a sensor unit. The sensor unit includes a first sensor unit 364 arranged on the clamp-holder upper end cover 241 and a second sensor unit 365 arranged on the clamp-holder lower end cover 242, a first wiring of the first sensor unit 364 is connected to the second upper joint 2410, and a second wiring of the second sensor unit 365 is connected to the second lower joint 2420. One end of the first data line 362 is connected to the data acquisition unit 361, and the other end passes through the first pipeline channel 211 and is connected to the first upper joint 2101; and one end of the second data line 363 is connected to the data acquisition unit 361, and the other end passes through the second pipeline channel 221 and is connected to the first lower joint 2201. When the first upper joint 2101 is docked with the second upper joint 2410, the first data line 362 communicates with the first wiring; and when the first lower joint 2201 is docked with the second lower joint 2420, the second data line 363 communicates with the second wiring. In this way, the data acquisition unit 361 can receive sensing data of the first sensor unit 364 and the second sensor unit 365 through the first data line 362 and the second data line 363, respectively. As an example, the sensor unit may include a temperature sensor, a resistivity sensor, a wave-velocity sensor, and the like. In this embodiment, a first data line 262 extending out of the first pipeline channel 211 is arranged spirally, and a second data line 263 extending out of the second pipeline channel 221 is arranged swirlingly.

With the solution in this specification, in each CT scan, data obtained after 3D reconstruction are subjected to grayscale threshold segmentation, sediment particles, water, a hydrate, and methane are separately extracted, and parameters such as hydrate saturation in a sediment are obtained through digital core calculation. Moreover, the sensor units arranged on the clamp-holder upper end cover and the clamp-holder lower end cover are used, for example, the overall resistivity in the clamp holder is measured using electrodes, and the overall acoustic wave velocity of a sediment in the clamp holder is measured using an acoustic wave transmitting and receiving probe, such as to obtain the resistivity and wave velocity characteristics of different hydrate sediments under different saturation levels, which provides a reference for actual downhole logging.

In summary, the experimental system provided in this embodiment can make a confining pressure liquid enter the confining pressure space through the confining pressure pipeline system to realize an in-situ environment, that is, to realize the control of artificial sediment confining pressure and temperature; during a hydrate synthesis process, real-time gas supply/water supply to the reactor and micro-CT scanning are used in combination with acoustic wave and resistivity probes to achieve intuitive 3D characterization and indirect measurement on the phase transition process and saturation difference of a hydrate sediment in pores at various stages of hydrate synthesis; the hydrate decomposition is observed by a heat injection/heating/depressurization/reagent injection method, and the micro-CT scanning is used in combination with acoustic wave and resistivity probes to achieve intuitive 3D characterization and indirect measurement on the saturation change of a hydrate sediment at various stages of hydrate decomposition; and water injection seepage and micro-CT scanning are used in combination with acoustic wave and resistivity probes to achieve intuitive 3D characterization and indirect measurement on the difference in effective permeability of a hydrate sediment at various stages of hydrate synthesis and decomposition.

In addition, the reactor of this embodiment can be adapted to a CT scanning device to realize the in-situ synthesis and decomposition of a hydrate and conduct a seepage experiment, and CT can be used to characterize the phase change and pore characteristics of an internal hydrate in real time. Parallel experiments can be conducted on multiple samples at the same time (by arranging multiple sets of clamp holders). In addition, a high-density metal scale 231 is attached to the reactor housing 23 to achieve X-ray visualization and facilitate the calibration of a position in the reactor during scanning selection and image processing. The interference of air on hydrate synthesis is eliminated by adding an evacuation system, and the evacuation system is used to check the air tightness of the system pipeline to improve the safety.

The solutions of the present application have been described in detail above with reference to the accompanying drawings. In the above examples, the description of each of the examples has a focus, and portions not described in detail in an example may refer to the description of other examples. Those skilled in the art should also know that the actions and modules involved in the description are not necessarily required by the present application. In addition, it can be understood that the steps in the method of the example of the present application may be sequentially adjusted, combined, and deleted according to actual needs, and the modules in the device of the example of the present application may be combined, divided, and deleted according to actual needs.

The examples of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed examples. It is apparent to those skilled in the art that many modifications and changes may be made without departing from the scope and spirit of the described examples. The terms used herein are selected to best explain principles of the examples, practical applications, or improvements to technologies in the market, or to enable other persons of ordinary skill in the art to understand the examples disclosed herein. 

What is claimed is:
 1. A multifunctional experimental system for in-situ simulation of a gas hydrate, comprising a computed tomography (CT) scanning device, a reactor, and a pipeline system, wherein the CT scanning device is provided with a rotating platform, the reactor is placed on the rotating platform, and the rotating platform is configured to drive the reactor to rotate; the reactor comprises: a reactor upper end cover, wherein a first pipeline channel is formed at a top of the reactor upper end cover, at least one upper groove is formed at a bottom of the reactor upper end cover, and a first upper joint is arranged in the upper groove; a reactor lower end cover, wherein a second pipeline channel is formed at a side of the reactor lower end cover, at least one lower groove is formed at a top of the reactor lower end cover, and a first lower joint is arranged in the lower groove; and a reactor housing, wherein two ends of the reactor housing are configured to be respectively fixed to the reactor upper end cover and the reactor lower end cover to form a sealed first accommodating cavity, and the first accommodating cavity is provided with at least one clamp holder; the clamp holder has a second accommodating cavity, a top end of the clamp holder is provided with a second upper joint, and a bottom end of the clamp holder is provided with a second lower joint; and the top end of the clamp holder is configured to be embedded into the upper groove to make the second upper joint in butt communication with the first upper joint, and the bottom end of the clamp holder is configured to be embedded into the lower groove to make the second lower joint in butt communication with the first lower joint; in the pipeline system, a first part of an upper pipeline extends into the first pipeline channel and is configured to communicate with the first upper joint, and a first part of a lower pipeline extends into the second pipeline channel and is configured to communicate with the first lower joint; in the pipeline system, a second part of the upper pipeline extends out of the first pipeline channel and is arranged spirally, and a second part of the lower pipeline extends out of the second pipeline channel and is arranged swirlingly; and the clamp holder comprises: a clamp-holder upper end cover, wherein the second upper joint is arranged at a top of the clamp-holder upper end cover; a clamp-holder lower end cover, wherein the second lower joint is arranged at a bottom of the clamp-holder lower end cover; and a porous shell, wherein two ends of the porous shell are configured to be respectively fixed to the clamp-holder upper end cover and the clamp-holder lower end cover to form the sealed second accommodating cavity, and the second accommodating cavity is pre-filled with a sediment sample; and a rubber sleeve is attached to an inner wall of the porous shell, and a confining pressure space is formed between an outer wall of the porous shell and an inner wall of the reactor housing.
 2. The multifunctional experimental system according to claim 1, wherein the first upper joint and/or the second upper joint are/is provided with a first locking mechanism, and the first locking mechanism is configured to lock the first upper joint and the second upper joint after the first upper joint is docked with the second upper joint; and the first lower joint and/or the second lower joint are/is provided with a second locking mechanism, and the second locking mechanism is configured to lock the first lower joint and the second lower joint after the first lower joint is docked with the second lower joint.
 3. The multifunctional experimental system according to claim 1, wherein an inner wall of the upper groove is provided with a third locking mechanism; after the clamp holder is embedded into the upper groove, the first upper joint is docked with the second upper joint and the third locking mechanism is configured to be locked with an upper part of the porous shell; and an inner wall of the lower groove is provided with a fourth locking mechanism; and after the clamp holder is embedded into the lower groove, the first lower joint is docked with the second lower joint and the fourth locking mechanism is configured to be locked with a lower part of the porous shell.
 4. The multifunctional experimental system according to claim 1, wherein a first target-shaped groove is formed at an inner side of the clamp-holder upper end cover, and after the second upper joint is in butt communication with the first upper joint, a gas and/or a liquid flowing in through the second upper joint evenly diffuse to the second accommodating cavity along the first target-shaped groove; and a second target-shaped groove is formed at an inner side of the clamp-holder lower end cover, and after the second lower joint is in butt communication with the first lower joint, a gas and/or a liquid flowing in through the second lower joint evenly diffuse to the second accommodating cavity along the second target-shaped groove.
 5. The multifunctional experimental system according to claim 1, wherein the reactor further comprises a rubber sealing sleeve, and the rubber sealing sleeve is configured to achieve a sealing between the porous shell and the upper groove and a sealing between the porous shell and the lower groove after the clamp holder is embedded into the upper groove and the lower groove; and/or, the reactor housing and the porous shell of the clamp holder are each made of a polymer composite, and a metal scale is formed on an outer surface of the reactor housing; and/or, a number of the upper grooves and a number of the lower grooves are equal to a number of the clamp holders, and when there are a plurality of clamp holders, an outer surface of a porous shell of each of the plurality of clamp holders is marked with a number made of a metal.
 6. The multifunctional experimental system according to claim 1, wherein the pipeline system comprises a confining pressure liquid pipeline system, wherein the confining pressure liquid pipeline system is configured to inject a confining pressure liquid of a preset temperature and a preset pressure into the confining pressure space; a first part of a first confining pressure liquid pipeline of the confining pressure liquid pipeline system extends into the confining pressure space through the first pipeline channel, and a first part of a second confining pressure liquid pipeline of the confining pressure liquid pipeline system extends into the confining pressure space through the second pipeline channel; and a second part of the first confining pressure liquid pipeline extends out of the first pipeline channel and is arranged spirally, and a second part of the second confining pressure liquid pipeline extends out of the second pipeline channel and is arranged swirlingly.
 7. The multifunctional experimental system according to claim 6, wherein the pipeline system further comprises: a gas delivery pipeline system, wherein the gas delivery pipeline system is configured to deliver a gas from two ends of the clamp holder to the second accommodating cavity of the clamp holder, wherein a first gas delivery pipeline of the gas delivery pipeline system communicates with the upper pipeline through a four-way valve, and a second gas delivery pipeline of the gas delivery pipeline system communicates with the lower pipeline through a three-way valve; a water delivery pipeline system, wherein the water delivery pipeline system is configured to deliver a liquid from the bottom end of the clamp holder to the second accommodating cavity of the clamp holder, wherein a water delivery pipeline of the water delivery pipeline system communicates with the lower pipeline through the three-way valve; and a gas/liquid recovery pipeline system, wherein the gas/liquid recovery pipeline system is configured to recover a gas and/or a liquid decomposed from the second accommodating cavity of the clamp holder, wherein a gas/liquid recovery pipeline of the gas/liquid recovery pipeline system communicates with the upper pipeline through the four-way valve.
 8. The multifunctional experimental system according to claim 7, wherein the pipeline system further comprises an evacuation pipeline system, wherein the evacuation pipeline system is configured to evacuate each pipeline of the pipeline system; and an evacuation pipeline of the evacuation pipeline system communicates with the upper pipeline through the four-way valve.
 9. The multifunctional experimental system according to claim 8, wherein the experimental system further comprises a data acquisition system; wherein the data acquisition system comprises: a sensor unit, wherein the sensor unit comprises a first sensor unit arranged on the clamp-holder upper end cover and a second sensor unit arranged on the clamp-holder lower end cover, a first wiring of the first sensor unit is connected to the second upper joint, and a second wiring of the second sensor unit is connected to the second lower joint; a first data line, wherein a first end of the first data line is connected to the data acquisition unit, and a second end of the first data line passes through the first pipeline channel and is connected to the first upper joint; and a second data line, wherein a first end of the second data line is connected to the data acquisition unit, and a second end of the second data line passes through the second pipeline channel and is connected to the first lower joint; wherein when the first upper joint is docked with the second upper joint, the first data line is connected to the first wiring; when the first lower joint is docked with the second lower joint, the second data line is connected to the second wiring; a part of the first data line extends out of the first pipeline channel and is arranged spirally, and a part of the second data line extends out of the second pipeline channel and is arranged swirlingly.
 10. The multifunctional experimental system according to claim 2, wherein the pipeline system comprises a confining pressure liquid pipeline system, wherein the confining pressure liquid pipeline system is configured to inject a confining pressure liquid of a preset temperature and a preset pressure into the confining pressure space; a first part of a first confining pressure liquid pipeline of the confining pressure liquid pipeline system extends into the confining pressure space through the first pipeline channel, and a first part of a second confining pressure liquid pipeline of the confining pressure liquid pipeline system extends into the confining pressure space through the second pipeline channel; and a second part of the first confining pressure liquid pipeline extends out of the first pipeline channel and is arranged spirally, and a second part of the second confining pressure liquid pipeline extends out of the second pipeline channel and is arranged swirlingly.
 11. The multifunctional experimental system according to claim 3, wherein the pipeline system comprises a confining pressure liquid pipeline system, wherein the confining pressure liquid pipeline system is configured to inject a confining pressure liquid of a preset temperature and a preset pressure into the confining pressure space; a first part of a first confining pressure liquid pipeline of the confining pressure liquid pipeline system extends into the confining pressure space through the first pipeline channel, and a first part of a second confining pressure liquid pipeline of the confining pressure liquid pipeline system extends into the confining pressure space through the second pipeline channel; and a second part of the first confining pressure liquid pipeline extends out of the first pipeline channel and is arranged spirally, and a second part of the second confining pressure liquid pipeline extends out of the second pipeline channel and is arranged swirlingly.
 12. The multifunctional experimental system according to claim 4, wherein the pipeline system comprises a confining pressure liquid pipeline system, wherein the confining pressure liquid pipeline system is configured to inject a confining pressure liquid of a preset temperature and a preset pressure into the confining pressure space; a first part of a first confining pressure liquid pipeline of the confining pressure liquid pipeline system extends into the confining pressure space through the first pipeline channel, and a first part of a second confining pressure liquid pipeline of the confining pressure liquid pipeline system extends into the confining pressure space through the second pipeline channel; and a second part of the first confining pressure liquid pipeline extends out of the first pipeline channel and is arranged spirally, and a second part of the second confining pressure liquid pipeline extends out of the second pipeline channel and is arranged swirlingly.
 13. The multifunctional experimental system according to claim 5, wherein the pipeline system comprises a confining pressure liquid pipeline system, wherein the confining pressure liquid pipeline system is configured to inject a confining pressure liquid of a preset temperature and a preset pressure into the confining pressure space; a first part of a first confining pressure liquid pipeline of the confining pressure liquid pipeline system extends into the confining pressure space through the first pipeline channel, and a first part of a second confining pressure liquid pipeline of the confining pressure liquid pipeline system extends into the confining pressure space through the second pipeline channel; and a second part of the first confining pressure liquid pipeline extends out of the first pipeline channel and is arranged spirally, and a second part of the second confining pressure liquid pipeline extends out of the second pipeline channel and is arranged swirlingly. 